Does 1/2 amount of Levain equal double amunt of bulk fermenting?
Yep, the title says it all.
I tried to get the breads more sour and flavourfull so I used 1/2 amount (90 g) of levain in order to increase bulk fermentation time.
Ive read on this forum, that a small amount of Levain (7-10%) and longer bulk fermentation (12 hours) at 70 deg F, adds to the sourness. Naturally I had to try that. So I cut my normal amount of Levain in half and tried to extend the bulk ferment to 12 hours at 68 deg F.
That experiment didnt go all that well. After 8-9 hours, the dough was so fermentet, that I got a little scared of overfermenting. So I shaped the breads and threw them in the oven one hour later. I wanted to retard them overnight in the fridge, but that would have given me pancakes... I guess.
The breads came out ok. A little to dense crumb with some larger holes, that (I assume) came from rushed and sloppy shaping.
Anyway this proces made me wonder... can I cut down the Levain to 1/2 of my normal amount and double the bulk fermentation compared to my normal bulk fermentation time?... Is it really as simple as that?
The starter is a living entity, teeming with bacteria and yeast. These biological systems follow a geometric growth curve, meaning that in a given period of time the population will double. What does this mean to sourdough bakers? The time to double the population is dependent on the rate that the starches are consumed to form sugars and other byproducts, which is in turn dependent on the activity and blend of bugs in the starter, the type and amount of foods available to them, etc.. This is complicated by at least two factors: first, the acidic byproducts (lactic acid and acetic acid, which provide the sour to the sourdough) will accumulate and eventually slow the fermentation rate by limiting the population growth, and also kill off some of the yeast cells, limiting the oven bloom of your loaf. Secondly, proteases, which are enzymes that attack proteins, will break down the gluten structure giving you a soupy dough. It sounds like you reached this point.
Here's an arbitrary example. Say a newly fed levain peaks in 4 hours. That loosely approximates the population doubling time. Go longer and the food remaining starts to decline while the proteases accumulate. However, if you mix your dough at the peak, it provides lots more food to allow the bugs to grow, and their number will continue to double every 4 hours. But unfortunately, this doesn't translate into a bread baking protocol.
I have not been able to find or come up with any formula to estimate how the preferment percentage affects the bulk ferment. Whole grain flours ferment more quickly than refined flours. Some grains, durum wheat comes to mind, ferment much more quickly than hard red wheat used in bread flours. Temperature has a huge affect on fermentation rate. There have been some posts that show the relative growth curves of bacteria and yeast at different temperatures, but I can't find them at the moment. In general, as the saying on TFL goes, watch the dough, not the clock.
Probably not exactly the answer you were seeking, but I hope it helps.
-Brad
Brad and JM. All thsese numbers makes my head spin, Ill need a few moment to make sense out of it :-)
Yes I feared that it wasnt that straightforeward. But not much is for a newb in this sourdough world.
Numbers, science behind sourdough and fermentation also confuses me fusan. I am not able to calculate a recipe and workout the exact amount of time I have for bulk fermentation + final proofing. But with lots of trial and error behind me I now have a fair idea of percentages and how long I have. Although I might not be maximising the starters potential as I always err on the side of caution. As long as I get it all done before it turns to mush (which I have done plenty of times). The way how I understand it is as follows...
That's it in a nutshell. How fast yeast multiplies and if simply halving it = twice the amount of fermentation I've yet to master this.
So when it comes to things like "how long do you have for how much starter" there is trial and error till you get to "know" how quick your starter works depending on ratio!
OR... you can go by feel and how it looks. A good rule of thumb is double for bulk fermentation and then almost doubled for final proofing. Which is fine if you can keep an eye on it.
that theres no shortcuts with sourdough. It depends on when I feed it. Sometimes I feed it when its at the top and other times, when I want it more sour, Ill wait a couple of hours more between each feeding. This also have an effect on the fermentation of the final dough. With last bake I used fine grined whole wheat and the result was way different than usual. I learned that whole wheat just ferments faster than normal white wheat. A while ago I started to log all my baking and maybe someday I can see a pattern with my sourdough, levain and breaddough. But right now its still a mystery.
Somewere along the way, because theres so many factors, Ill need to rely on my experience.
Also don't forget all our starters are unique. Many times I've followed a recipe which calls for an all night ferment where my starter needs less time. I've ruined many a recipe by doing a recommended all night ferment but have woken up to a blob instead of a dough. Final Proofing too... Emmanuel Hadjiandreou's book "how to make bread" recommends in his sourdough recipes 3-6 hours depending on how active your starter is but when I follow it I always find closer to 2.5 hours is all my starter needs. There are so many variables. And even if it makes sense for half the starter = twice the length of fermentation your feeding schedule might've changed the starter and flours will make a difference. But all things being equal I don't think half starter = double ferment time like Brad said.